Online Student Book

 

Thresholds and Toxicology

Thresholds and Toxicology Book Cover

Thresholds and Toxicology is a SEPUP module designed for use in grades 7–12. The module contains a series of 10 activities that provide approximately 3 weeks of instruction

News

Looks Like Sugar, Tastes Like Sugar…

A new no-calorie sweetener may be in the food you eat. It sold under the brand name of Splenda®. It was first discovered in 1976 and approved for limited use in the United States in 1998. In July 1999, it received approval for unlimited use. Splenda®, or sucralose, is made from sugar. It is made by replacing three hydrogen–oxygen groups on the sugar molecule with three chlorine atoms. This slight chemical change means that the human body cannot break it down. As a result, a person would not get calories from it.

Since its discovery, there have been more than 100 scientific studies on it. Causing virtually no side effects, it has been proven to be safe in animal and human trials. Unlike other artificial sweeteners, it can be measured in quantities similar to sugar and stored for long periods of time. It also holds up to heat, which means that it doesn’t lose its sweetness in cooking.

 

Even Low Levels of Lead Affect IQ

It has been known for a long time that exposure to lead lowers IQ (intelligence quotient). It was widely held that 10 micrograms of lead per deciliter of blood or more could affect a child’s development. A five-year study sponsored by the National Institute of Health now suggests that much lower lead levels can affect IQ.

The study focused on 172 children in Rochester, New York. The amount of lead in their blood was measured at 6, 12, 18, 24, 36, 48, and 60 months, and they took IQ tests at ages 3 and 5. Other variables that affect IQ, such as birth weight, income, education, and amount of stimulation in the home, were controlled. "In this sample of children we find that most of the damage to intellectual functioning occurs at blood lead concentrations that are below 10 micrograms per deciliter," said Richard Canfield of Cornell University and the primary author of the study.

The study concluded there was no safe threshold for lead exposure.